Singleton cde

public class SingleTon {
private static SingleTon singleTon = null;

private SingleTon() {
System.out.println("instance...");
}

public static SingleTon getInstance() {
if (singleTon == null) {
singleTon = new SingleTon();
return singleTon;
}
return singleTon;
}

public void sum() {
System.out.println("services");
}

}